Expanding wild explained
An expanding wild is a wild symbol that grows to cover every position on its reel when it lands, or when a feature activates it. Because every payline passes through every reel, a fully expanded wild takes part in all of a slot’s lines at once, which is why the feature is so common in classic five-reel games.
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Key takeaways
- An expanding wild fills its whole reel, so it sits on every payline.
- Some expand whenever they land; others only expand in a feature.
- Expanding wilds differ from expanding symbols, which pay as themselves.
- Frequent expanding wilds usually mean small, regular wins and lower volatility.
- Behaviour
- Grows to fill its entire reel
- Usual reels
- Middle reels, often 2 to 4
- Often paired with
- A respin while the wild holds
- Best-known example
- Starburst (NetEnt)
- Close relative
- Expanding symbol in book slots
What an expanding wild is
A normal wild symbol occupies one position and helps only the lines that pass through that position. The expanding version starts the same way but then stretches up and down until its entire reel is wild. On a 5×3 slot, that turns one wild into three; on a game with taller reels, into four, five or more.
The trigger varies. In some games every wild expands as soon as it lands. In others it expands only when it would complete a win, only during free spins, or only as part of a random feature.
Why a full wild reel touches every payline
A payline is a path that visits each reel exactly once. That simple rule is the key to expanding wilds: if every position on reel 3 is wild, every line must pass through a wild on reel 3, whatever route it takes. A single wild in the middle row of reel 3 sits on only some lines; the expanded version sits on all of them.
| Situation | Positions covered on the reel | Lines that pass through a wild |
|---|---|---|
| Single wild, one position | 1 of 3 | Only the lines crossing that cell |
| Expanded wild, full reel | 3 of 3 | All 10 |
| Two expanded wilds on reels 2 and 4 | 6 of 6 | All 10, with two wild positions each |
Worked example: at a £1 stake on a 10-line game (10p per line), suppose reel 3 expands and five lines now show three matching low symbols, each paying 5 times the line bet. That is 5 × 50p = £2.50 from a spin that might otherwise have paid one line or none. The figures are illustrative, but the pattern of several small line wins at once is typical of how expanding wilds pay.
Case study: Starburst’s expanding wild respins
Starburst is the slot most players picture when they hear the term. Its wild can land only on reels 2, 3 and 4. The sequence works like this:
- A wild lands on reel 2, 3 or 4 and expands to fill the reel.
- Wins are paid, and the expanded reel stays in place for a respin.
- The other reels spin again. If another wild lands on a free middle reel, it also expands and holds.
- Each new wild triggers another respin, up to a maximum of three, when all three middle reels are wild.
Starburst also pays both ways across its 10 paylines, so a wild reel helps wins starting from either side. The result is a low-volatility game with a 96.09% RTP and a 500x max win: frequent, modest returns rather than rare large ones. Its sequel Starburst XXXtreme adds multipliers to the expanding wilds and pushes the max win to 200,000x, with high volatility to match.
Expanding wild vs expanding symbol
The two are easy to mix up because both fill a reel. The difference is what they become once expanded.
| Expanding wild | Expanding symbol | |
|---|---|---|
| What fills the reel | Wilds | One regular paying symbol |
| Helps other symbols win? | Yes, by substitution | No, it pays as itself |
| Typical setting | Base game and respins | Free spins in book-style slots |
| Example | Starburst | Book of Dead free spins |
In Book of Dead, one symbol is picked at random when free spins begin and expands whenever it lands during the round. It does not substitute for anything; it simply covers reels with copies of itself. Eye of Horus sits between the two: its Horus wild expands to fill the reel and, in free spins, also triggers a symbol upgrade.
Random wild reels and other expanding variations
Some slots skip the landing step and simply turn whole reels wild at random. In Thunderstruck II, the Wildstorm feature can strike on any base game spin and turn up to all five reels fully wild. Other games expand wilds only upwards or downwards, or expand them across rows instead of reels on wider grids.
More examples, grouped by how their wilds behave, are on our expanding wild slots page.
What expanding wilds mean for your session
Because an expanding wild usually produces several small line wins rather than one large one, slots that lean on them tend to feel steadier. That does not change the long-run cost, which is set by the RTP: at 96.09%, 200 spins at 10p (£20 staked) carry a theoretical return of about £19.22. Short sessions will vary around that, and over time losses are the expected outcome.
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Frequently asked questions
What is an expanding wild in slots?
An expanding wild is a wild symbol that grows to cover its entire reel. Once expanded, it substitutes for regular symbols on every position of that reel, so it takes part in every payline the slot has. Some expanding wilds grow every time they land, others only when completing a win or during a bonus round. They are often combined with a respin, where the wild reel stays in place while the others spin again. Starburst is the best-known example. A related idea, the sticky wild, keeps wilds in place across several spins.
How do Starburst expanding wilds work?
Starburst wilds can only land on reels 2, 3 and 4, and whenever one does, it expands to fill the reel and triggers a respin. The wild reel stays fixed while the other reels spin again. If another wild lands on an uncovered middle reel during the respin, it also expands and awards a further respin, up to three in total. Starburst’s ten lines pay both ways, so each wild reel helps wins from left and right. The game is rated low volatility; our volatility guide explains what that means for a session.
Is an expanding wild the same as an expanding symbol?
No. The wild version fills its reel with wilds that substitute for other symbols. An expanding symbol fills its reel with copies of one regular paying symbol, which pays as itself rather than helping others. Expanding symbols are the signature of book-style slots, where one symbol is chosen at random when free spins start and expands whenever it lands in the round. Book of Dead and Legacy of Dead both use this. The two features look similar on screen but work very differently in the maths.
Do expanding wilds make a slot pay more?
Not over the long run. A slot’s RTP is fixed by its design, and the expanding wilds are already part of that calculation. If wilds expand often, the developer sets symbol payouts lower so the total return stays at the published figure. What expanding wilds do change is how wins arrive, usually as several small line wins at once rather than rare large ones. That is why slots built around them often have low or medium volatility and modest maximum payouts. Our max win entry explains how payout caps are set.
Can an expanding wild appear on any reel?
It depends on the game. Many slots restrict expanding wilds to the middle reels, such as reels 2, 3 and 4, because a wild on reel 1 would affect every win in a left-to-right game and change the maths too much. Others allow wilds on all reels but only expand them in certain conditions. The paytable or rules screen lists the reels each wild can land on. For a broader view of how features are set off, see our guide to how slot features trigger.
Are expanding wild slots good for low stakes?
They can suit low-stake play because the frequent small wins tend to stretch a budget further than a high-volatility game would, though nothing changes the fact that the house edge applies and losses are the likely result over time. A 10p stake on a low-volatility expanding wild game will usually see the balance move gently up and down. If you want rarer, larger swings, look for games that pair expanding wilds with multipliers. Our page on how to choose a slot walks through matching a game to your budget.